Photoelectric transducer element including a heterojunction formed by a photoelectric transducer film and an intermediate film having a larger energy gap than the photoelectric transducer film

ABSTRACT

A photoelectric transducer element having high photo and spectral sensitivity in which a material with an energy band gap larger than that of a photoelectric transducer film is interposed between the photoelectric transducer film and a transparent conductive film.

United States Patent 1191 Fukai et a1.

[ 1 Dec. 31, 1974 Matsushita Electric Industrial Co. Ltd., Kadoma-shi,Osaka, Japan Filed: Nov. 6, 1972 Appl. 010.; 304,050

Assignee:

Foreign Application Priority Data Nov. 9, 1971 Japan 46-89622 Dec. 29,1971 Japan 47-3265 Sept. 25, 1972 Japan 47-96428 US. Cl 313/94, 252/623ZT, 357/16,

357/30, 357/61 Int. Cl. H01j 39/06, H011 9/00 Field of Search 313/94,96, 65 AB;

317/235 AC, 235 NA, 235 AP, 235 A0; 250/211 J; 338/15; 252/623 ZT [56]References Cited UNITED STATES PATENTS 3,287,611 11/1966 Bockemuehl317/235 AQ 3,346,755 10/1967 Dresner 313/94 3,405,298 lO/1968 Dresner317/241 OTHER PUBLICATIONS Morehead et a1., Efficient, VisibleElectroluminescence From p-n junctions in Zn Cd Te App Physics Letters,Vol. 5, 1964, pp. 53-54.

Abrikosov et a1., Semiconducting lI-Vl, lV-Vl &

V-VI, Compounds Plenum press, N.Y., 1969, pp. 26-28, QC612, S4P6.Tansley, T. L. Heterojunction Properties, Chapt. 6 of Semiconductors &Semimetals, Academic Press, N.Y. & London, 1971, Vol. 7, part A. pp.299-309 QC612, S4W5.

Primary Examiner-lames W. Lawrence Assistant ExaminerWm. H. PunterAttorney, Agent, or Firm-Stevens, Davis, Miller & Mosher 57] ABSTRACT Aphotoelectric transducer element having high photo and spectralsensitivity in which a material with an energy band gap larger than thatof a photoelectric transducer film is interposed between thephotoelectric transducer film and a transparent conductive film.

11 Claims, 9 Drawing Figures SPECTRAL SENOSITIVITY (,u w) T APPLIEDVOLTAGE 30V PATENTEB UEC3 1 I974 SHEET 10F 5 FIG.2

6000 8000 o WAVE LENGTH (A) PAIENIEUHECBHBH 3.858.074

SHEET 2 UF 5 Xe LAMP LIGHT souRcE XAND FILTER F I 4 SHUTTER 5'ELECTROMAGNETIC RL AMPL- OSCILLOGRAPH SYNCHROSCOPE VT I 5 aw F l G. 510) E j 30 v l "5- EE DU o 'z'o'4b'eb'o' n e e COMPOSITION F l G. 6

(XIO A 5 o 0.36 Lux E E 30 V lhi as 2 0 SE W-LAMP I: 0.0

0 2O 4O 6O 8O ZnTe COMPOSITION PATENTEDBEBII 1 IBM 3, 858,074

SHEET 3 OF 5 FIG. 7

APPLIED VOLTAGE 30V SPECTRAL SENSITIVITY [LA/PW) S WAVE LENGTH 1KPATENTEDIJEBIH I974 3,858,071}

SHEET 0F 5 FIG. 8 V

(Znos Cdo.4Te) (In2Te3) APPLIED VOLTAGE 30V SPECTRAL SENOSITIVITY(/LA/FW) T WAVE LENGTH Z PATENTEU 1 I974 SPECTRAL SENSITIVITY #MLW)SHEET 5 i'lF 5 F I G. 9

APPLIED VOLTAGE 30v WAVE LENGTH (,3)

PHOTOELECTRIC TRANSDUCER ELEMENT INCLUDING A HETEROJUNCTION FORMED BY APHOTOELECTRIC TRANSDUCER FILM AND AN INTERMEDIATE FILM HAVING A LARGERENERGY GAP THAN THE PHOTOELECTRIC TRANSDUCER FILM The present inventionrelates to a photoelectric transducer element, or more in particular toa photoelectric transducer element suitably used as a target for animage pickup tube.

CdS, CdSe and mixed crystals thereof are well known as materialssuitable for a photoelectric transducer ele' ment. In spite of theirhigh sensitivity, however, they can not be used as a target of an imagepickup tube due to considerable dark current accompanying them and theirslow responsiveness to light. Also, their spectral sensitivity is lowfor wavelengths other than those corresponding to their energy bandgaps, and materials with a spectral sensitivity curve which is flat overthe entire range of visible light have yet to be developed.

Well-known conventional materials used as targets for image pickup tubesinclude a film of antimony trisulfide Sb S for vidicons, lead oxide PbOfor PbO vidicons and a silicon photodiode array for silicon vidicons.All of these materials, however, have their problem points as mentionedbelow.

1. Vidicons The vidicon has the sensitivity in the order of 200 to 300ptA/lm and the dark current of 20 nA per one'inch vidicon, and is usedas a camera for industrial television, but its low sensitivity limitsthe images capable of being picked up to those of brightness in theorder of 5 1x or more. Another disadvantage of the vidicon is aconsiderable amount of undesirable afterimage and lay-image accompanyingthe pickup operation, making it unsuitable for use with a color imagepickup tube for television broadcasting.

2. PbO vidicon With a very small amount of dark current of 0.2 nA/l.5inches and a little lay-image, this is widely used with an image pickuptube for television broadcasting. But its sensitivity is as low as 300uA/lm which is a little higher than that of the vidicon but stillinadequate. Since this has no spectral sensitivity for a red light withwavelength of 650 nm or more, the use of this PbO vidicon for the redcolor image pickup tube of the threetube type camera requires PbS to beadded to PbO so as to increase its sensitivity to about 850 nm. Thesensitivity and lag-image of this image pickup tube, however, do notcoincide with those of the other tubes of the camera, resulting in thelack of balance among the three tubes. Further, it is impossible to usethis image pickup tube for a singledube camera since it has only a smallrange of spectral sensitivity.

3. Si vidicon This image pickup tube has the advantages of a sensitivity20 times that of the vidicon and the absence of undesirable after-image.But is characteristics associated with lag-images and resolution areinferior to those of the PhD vidicon, making it unsuitable for use withan image pickup tube for television broadcasting. Another disadvantageof this tube lies in that the peripheral portions of an image of a verybright object are blurred thereby to undesirably enlarge the image to asize two or three times the original image.

Accordingly, it is an object of the present invention to provide aphotoelectric transducer element suitable for the target of an imagepickup tube and having a high sensitivity and superior property ofspectral sensitivity.

The photoelectric transducer element according to the present inventionis characterized in that a material with an energy band gap larger thanthat of a photoelectric transducer film is interposed between atransparent conductive film and the photoelectric transducer film.

The above and other objects, features and advantages will be madeapparent by the detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a sectional view showing an embodiment of the presentinvention;

FIG. 2 is a diagram comparing the spectral sensitivity of aphotoelectric transducer element with a ZnSe film interposed between thetransparent conductive film and the photoelectric transducer film withthat of a photoelectric transducer element without any ZnSe filminterposed;

FIG. 3 is a diagram showing the spectral sensitivity ofZnSe-Zn,,Cd,.,,Te;

FIG. 4 is a diagram showing the principle on which the responsiveness tolight is measured;

FIG. 5 is a graph showing how the dark current varies with thecomposition of ZnSe-(Zn,,Cd,. u )0.9s( 2 a)0.o.-s;

FIG. 6 is a diagram showing how the photoelectric current varies withthe composition of the ZnSeu 1-u )o.95( z alopsi FIG. 7 is a diagramshowing the spectral sensitivity of the photoelectric transducer elementconsisting of Zny l-J/ )0.95( 2 3)0.05;

'FIG. 8 is a characteristic diagram showing the spectral sensitivity ofthe photoelectric transducer element consisting of ZnSe-(Zn Cd Te),(lnTe and FIG. 9 is a characteristic diagram showing the spectralsensitivity of the photoelectric transducer element Consisting Of ZIISSC AZn CCl T) I11 Tc Referring to FIG. 1, a transparent conductive film2 of, say, In O or SnO is formed on a glass substrate 1, and aphotoelectric transducer film 4 is formed on the transparent conductivefilm 2 with an intermediate film 3 therebetween having an energy bandgap larger than that of the photoelectric transducer film 4. Aheterojunction is formed by the intermediate film 3 and thephotoelectric transducer film 4.

The facts that must be taken into consideration in selecting thematerial for the intermediate film 3 are (1) that the lattice constant,crystal structure and the coefficient of thermal expansion of theintermediate film approximate those of the photoelectric transducer filmand (2) that the band structure of the intermediate film 3 and thephotoelectric transducer film are capable of being connected smoothlywith each other when they are bonded together. These conditions must bemet to improve the photoelectric transducing efficiency by improving thecrystal quality of the surface of that side of the photoelectrictransducer film from which light enters and thereby reducing the surfacestate due to lattice defects. Light with a wavelength shorter than onecorresponding to the energy band gap of the photoelectric transducerfilm is absorbed by the photoelectric transducer film at a portion verynear its surface. If this portion has a low crystal quality with manyrecombination centers present in that portion, a low photoelectrictransducing-efficiency results.

The results of experiments conducted by the inventors show that theenergy band gaps of the intermediate film 3 and the photoelectrictransducer film 4 determine the limits of short and long wavelengthrespectively for which the spectral sensitivity is effective. FIG. 2shows the results of the test in which the characteristic of thephotoelectric transducer film 4 of (Zn Cd Te)0 9 (In Tc3)0 05 with theintermediate film 3 of ZnSe is compared with the photoelectrictransducer film of the same substance without the intermediate film 3 ofZnSe. In this figure, curve I is the case without any ZnSe film andcurve II with the ZnSe film. It will be easily understood from thisdrawing that curve II associated with the transducer film with the ZnSefilm represents a spectral sensitivity for short wavelengths much higherthan curve I showing the characteristic of the transducer film in theabsence of the ZnSe film. Also, it was found that the use of the ZnSefilm reduces the dark current. Further, as a result of comparison, on areplica photograph taken under the electronic microscope, between afirst photoelectric transducer element with the intermediate film ofZnSe laid between the glass substrate and the photoelectric transducerfilm of 500 A. ahd a second photoelectric transducer element without anyintermediate film, it was made clear that the grain size of thetransducer element with the ZnSe film is larger than that without anyZnSe film.

Before reference is had to embodiments of the present invention,explanation will be made below of the methods of manufacturing andmeasuring the characteristics of the photoelectric transducer elementwhich were commonly applied to all of the embodiments.

First, several depositing heaters are placed in a depositing means andsuch a depositing material as ZnS, ZnSe, ZnTe, CdTe, ln Te or theirsolid solution is applied to the heaters. By controlling the temperatureof the heaters, a solid solution of a desired composition is made. Theavailability of several heaters permits the manufacture of a compositefilm without affecting the vacuum condition. A glass substrate with thetransparent conductive film attached thereto is heated to 100 to 400Cthereby to deposit the solid solution of the above-mentioned compositionon it by evaporation. The resulting assembly is heated at 300 to 700Cfor from several minutes to several hours to produce a photoelectrictransducer element.

The dark current, photoelectric current, responsiveness to light andspectral sensitivity of the photoelectric transducer element thusproduced and with an electrode formed on that side having thephotoelectric transducer film were measured, the results of which are asfollows:

a. Spectral sensitivity An interference filter and a halogen lamp of3400K were used to measure the photoelectric current at regularintervals of 200 A. The amount of light applied to the specimen throughthe filter from a light source was measured by means of a thermopile.

b. Dark current and photoelectric current The current-voltagecharacteristic as well as the photoelectric current-illuminationcharacteristic were measured with the Electrometer Model 610C ofkeithley.

c. Responsiveness to light The response to light of an image pickup tubeis different from the photoconductive response of an element thereof inprinciple. The inventors have prepared an equivalent circuit whichrequires no electron beam, associated with a picture element of theimage pickup tube scanned by an electron beam, thereby to evaluate thecharacteristics of the image pickup tube through an element. Theprinciple of the evaluation is as shown in FIG. 4, in which thephotoelectric tube 5 is seen to be turned on and off by a light pulserwith a pulse width of 2 us at 60 Hz so as to apply an electron beam to apicture element at 60 Hz. Light of 0.4 lx was radiated on the elementfrom another light source of the halogen lamp of 3,400K so that theresponsiveness to light was measured with a shutter usually used forphotographing. The results of the measurements mentioned above coincidepretty well with those of measurements conducted on an image pickup tubeassembled from the element. The measurements were made in terms of arise and fall in 50 ms after the application and shutting off the lightrespectively.

d. Composition of the deposited film The composition of the depositedfilm was measured by solid mass analysis and activation analysis.

After measuring the characteristics of the element as above, thecharacteristics of the image pickup tube were determined as follows:

a. Dark current and photoelectric current:

A positive voltage was applied to that side of the image pickup tube towhich the transparent conductive film is attached, during the scanningby an electron beam, and a signal current taken out of the transparentconductive film was measured.

b. Lag-image and after-image:

A lag-image is a transient phenomenon representing the magnitude of asignal current remaining 50 ms after shutting light off. It occursduring the transition stage from a bright to dark state and is generallyexpressed in the percentage of a signal remaining at a time point 50 msafter shutting light off. An afterimage is a term indicating a timeperiod, as observed by a display monitor, needed for an image of anobject to be extinguished on a uniformly white background which waspicked up after picking up the object for a predetermined period of timeunder a standard pickup condition.

Embodiments of the present invention will be now explained. Embodimentl:

A photoelectric transducer element was used which comprises aheterojunction of an intermediate film of ZnS Se and a photoelectrictransducer film of Zn Cd fFe and experiments were conducted by varyingthe value y of Zn Cd Te while maintaining it of ZnS Se at zero.

As shown in FIG. 1, the assembly comprising a glass substrate 1 with atransparent conductive film 2 deposited on it was heated to andmaintained at the temperature of to 400C, andZnSe, that is ZnS,.Se withx at zero, is deposited by evaporation into the thickness of 0.02 to 2microns on the transparent conductive film 2 for 5 to 30 minutes. Onthis ZnSe film 3 is formed a solid solution 1 to 20 X 10" m thick byevaporation in a pair of melting pots containing ZnTe and CdTerespectively, while maintaining the temperature of the substrate at 150to 300C for 5 to 60 minutes. The value of y of the solid solution may bevaried by controlling the temperature of the melting pots. A composa lei the ralsensit vity o an bz s As can be seen from this figure, theeffect of spectral sensitivity extends further toward long wavelengths,the greater the amount of Cd relative to that of Zn. This is because theband gap is decreased with an increase in the amount of Cd. As a result,it is possible, by appropriately selecting the value of y, to obtain aphotoelectric transducer element with a spectral sensitivity over theentire range of visible light. I

The characteristics of a one-inch image pickup tube employing thephotoelectric transducer element according to the present invention arecompared with those of the conventional Sb S vidicon in Table 1 below.

It will be noted from this table that the sensitivity of the imagepickup tube according to the present invention is 2 or 3 times higherthan that of the conventional vidicon. Further, with the increase in theamount of Cd, the sensitivity is improved but the dark current is alsoincreased. There are less lagimage with the increase in the amount ofCd. All this tells that the photoelectric transducer element accordingto the present invention has a higher sensitivity and a broader range ofspectral sensitivity than the Sb S vidicon.

Furthermore, it was found that not only the spectral sensitivity forshort wavelength is improved but the range of spectral sensitivitybroadened and the sensitivity itself improved by replacing theintermediate film of ZnSe by a film of ZnS or the solid solutionconsisting of ZnS and ZnSe.

Embodiment 2 This embodiment has the same structure as embodiment 1,employing an intermediate film of ZnS Se as in embodiment 1 while it isdifferent from embodiment l in that Zn,Cd1.,,Te with In added thereto isused as a photoelectric transducer film. When the amount of In added tothe photoelectric transducer film of Zn Cd Te was changed from lXl0"/ccto 2Xl0 /cc, in the presence of an intermediate film of ZnSe, darkcurrent which occurred in the photoelectric transducer element is asshown in Table 2 below From this experiment, it is known that the darkcurrent tends to decrease with'theincrease in the amount of indiumaddedto the photoelectric transducer film.

It was found that, if the solid solution of Zn Cd Te remains unchanged,the spectral sensitivity also remains almost the same, but when theamount of indium added is higher than 10 /cc, the sensitivity curveextends toward long wavelength. The absolute value of the sensitivityhas sharply increased with the increase in the amount of in added. Therepresentative characteristics of a one-inch image pickup tube withatarget employing an element of the above-mentioned materials are shownin Table 3.

As'will be apparent from this table, the sensitivity rises considerablywith the increase in the amount of indium added, while dark currentdecreases, with the result that the S/N ratio for the photoelectrictransducer film obtained by adding indium in the amount of 2 l0 /cc inan evaporation source is improved by more than one order. Lag-imageshave remained almost the same.

As in embodiment l, the spectral sensitivity for short wavelength can beimproved and the range of wavelength over which the sensitivity iseffective can be broadened by replacing the intermediate film of ZnSewith a solid solution of ZnS Se As to the long wavelength side, thesensitivity may be extended to a desired A wavelength by changing theratio between Zn and Cd of the photoconductive film.

In the above-described experiment, the deposited film was made in thesame way as in embodiment l by adding indium to the Zn Cd Te throughthermal diffusion and the amount of indium is shown in terms of thequantity placed in an evaporation source. The results of mass analysisshow, however, that where a solid solution of Zn Cd Te containing indiumin the amount of 2 X lO lcc is used as an evaporation source, 3.2 atomicpercent of indium is contained in the deposited film. On the other hand,where a solid solution containing 2 X l0 /cc of indium is used, thedeposited film contains 0.02 atomic percent of indium. Embodiment 3 theintermediate filmland the photoelectric transducerfilm respectively asin embodiment 1. Experiments were conducted by varying the value of x, yand z separately. Since the structure and the method of manufacture ofthe photoelectric transducer element are the same as in embodiment 1,only the results of the experiment and advantages of the presentembodiment will be mentioned below. u l-u )0.95( 2 3)0.05

First, reference is made to a photoelectric transducer element with theintermediate film of ZnSe and a photoelectric transducer film of avarying ratio between Zn and Cd. With 5 percent of In Te added,experiments were conducted on the six values of y, i.e. 0.9, 0.8,

0.75, 0.7, 0.5 and 0.3, the results of which are shown below.

a. Dark current How dark current depends on the value of y is shown inFIG. 5. It is seen that the dark current becomes minimum when y is 0.7to 0.8 and it sharply increases at a t iise lx y rlbaaQ- or -8- b.Sensitivity The value y affects the sensitivity in such a manner asshown in FIG. 6. Although it must be admitted that differentsensitivities result from different methods of manufacturing theelement, it is apparent that the sensitivity rises with the decrease inthe value of y.

Table -Continued y 0.6 y 0.7 resolution 780 780 illumination (l E") r0.95 r 0.95

Table 4 The dark current tends to rise when 1 is smaller than 0.85,while it remains almost the same when z is between 1 and 0.85. Thesensitivity remains almost unchanged when 1 is between 1 and 0.85. Theresponse is quick for all of the values of Z and it is quicker thehigher the applied voltage. When z is smaller than 0.7, a phase of ln Tewas detected in the deposited film as a result of X-ray analysis. Thepresence of the phase causes a great dark current, thereby making theelement unsuitable for a target of the image pickup tube. Namely,'030mol percent of ln Te is suitable for the An example of responsivenessVolts Comp.

y=0.8 89/25 78/18 80/17 82/15 rise(%)/fall(%) y=0.7 86/17 81/13 85/11under 0.4 lx y=0.5 39/11 92/10 after msec.

Table 5 sensitivity (PA/1m) 4000 3840 dark current (nA) 5 4 lag-ima esl2 l4 residu images nil nil after-images nil nil target of the imagepickup tube. The sensitivity remains almost unchanged when Z is between1 and 0.85 as shown in FIG. 8. .r 1-.r'( o.s 0.4 )0.ss( 2 3)o.0s

Experiments were conducted for various values of x in ZnS Se For allvalues ofx including 0.5, 0.7 and 1.0 dark current, sensitivity andresponsiveness all remained almost the same as in the precedingembodiment, while the spectral sensitivity for short wavelength isincreased with the value of x as shown in FIG. 9. The element with x ofunity is suitable for an ultra-violet ray camera as it has asufficiently high sensitivity for the ultra-violet range.

It will be understood from above that the abovementioned image pickuptubes embodying the present invention have a higher sensitivity than theconventional vidicon and PbO vidicon, and the target includedin theembodiments has an almost flat curve of spectral sensitivity over theentire range of visible light, making it possible to apply the presentinvention to a singletube color image pickup tube.

Since the photoelectric transducer element according to the presentinvention is high both in photosensitivity and spectral sensitivity, itcan be used not only as a target of the image pickup tube but as aphotoelectric transducer film for electronic photograph and illuminationphotometer.

The reason why the present invention is characterized by a highphotosensitivity and spectral sensitivity is the interposition betweenthe transparent conductive film and the photoelectric transducer film ofan intermediate film with a larger energy band gap than thephotoelectric transducer film, which not only permits the portionsensitive to light, that is, the crystal structure at the junctionbetween the photoelectric transducer film and the intermediate film tobe improved but also allows light with a longer wavelength than the onecorresponding to the energy band gap of the intermediate film to enterthe photoelectric transducer film without loss.

As is apparent from the above explanation of the embodiments, thephotoelectric transducer element according to the present invention hasa higher photosensitivity as well as higher spectral sensitivity withoutany lag-images, residual images or undesirable after-image.

What is claimed is:

l. A photoelectric transducer element and a target for an image pickuptube using said element, comprising a photoelectric transducer film, atransparent conductive film, a material interposed between saidphotoelectric transducer film and said transparent conductive film, anda heterojunction of said photoelectric transducer film and saidmaterial, said material having a larger energy gap than saidphotoelectric transducer film, said photoelectric transducer filmcontaining Z n Cdb Te (0.l y0.9) as a main component, and said materialcontaining ZnS,Se,. gxg l) as a main component.

2. A photoelectric transducer element and a target for an image pickuptube using said element according to claim 1, wherein said photoelectrictransducer film containing Zn Cd,.,,Te (0.l gy; 0.9) as the maincomponent further contains indium added thereto.

3. A photoelectric transducer element and a target for an image pickuptube using said element according to claim 2, wherein said photoelectrictransducer film containing Zn Cd Te (0.1 gyg 0.9) as the main componentcontains 0.02 to 3.2 atomic percent of indium added thereto,

4. A photoelectric transducer element and a target for an image pickuptube using said element according to claim 1, wherein said photoelectrictransducer film containing Zn Cd,.,,Te (0.l yg 0.9) as the maincomponent further contains 30 mol% or less of a compound of In and Teadded thereto.

5. A photoelectric transducer element and a target for an image pickuptube using said element, comprising a photoelectric transducer film, atransparent conductive film, a material interposed between saidphotoelectric transducer film and said transparent conductive film, anda heterojunction of said photoelectric transducer film and saidmaterial, said material having a larger energy gap than saidphotoelectric transducer film, said photoelectric transducer filmcontaining Zn Cd Te (0 g y; 1) as a main component and furthercontaining 30 mol percent or less of a compound of In and Te addedthereto, said photoelectric transducer film having the formula and saidmaterial containing ZnS,,-Se,- ,-(0 5 x 2 l) as a main component.

6. A photoelectric transducer element and a target for an image pickuptube using said element according to claim 5, wherein x 0 and z 0.95.

7. A photoelectric transducer element and a target for an image pickuptube using said element, comprising a photoelectric transducer film, atransparent conductive film, a material interposed between saidphotoelectric transducer film and said transparent conductive film, anda heterojunction of said photoelectric transducer film and saidmaterial, said material having a larger energy gap than saidphotoelectric transducer film, said photoelectric transducer filmcontaining Zn Cd Te (0.5 i y 2 0.8) as a main component and furthercontaining 30 mol percent or less of a compound of ln and Te addedthereto, said photoelectric transducer film hhaving the formula and saidmaterial containing ZnSe as a main component.

8. A photoelectric transducer element and a target. for an image pickuptube using said element according to claim 5, wherein x 0 and y 0.6.

9. A photoelectric transducer element and a target for an image pickuptube using said element, comprising a photoelectric transducer film, atransparent conductive film, a material interposed between saidphotoelectric transducer film and said transparent conductive film, anda heterojunction of said photoelectric transducer film and saidmaterial, said material having a larger energy gap than saidphotoelectric transducer film, said photoelectric transducer filmcontaining Zn Cd Te as a main component and further containing 30 molpercent or less of a compound of [n and Te added thereto, saidphotoelectric transducer'film having the formula and said materialcontaining ZnSe as a main component.

10. A photoelectric transducer element and a target for an image pickuptube using said element according to claim 5, wherein y 0.6 and z 0.95.

11. A photoelectric transducer element and a target for an image pickuptube using said element according to claim 10, wherein x l.

1. A PHOTOELECTRIC TRANSDUCER ELEMENT AND A TARGET FOR A IMAGE PICKUPTUBE USING SAID ELEMENT, COMPRISING A PHOTOELECTRIC TRANSDUCER FILM, ATRANSPARENT CONDUCTIVE FILM, A MATERIAL INTERPOSED BEWTEEN SAIDPHOTOELECTRIC TRANSDUCER FILM AND SAID TRANSPARENT CONDUCTIVE FILM, ANDA HETEROJUNCTION OF SAID PHOTOELECTRIC TRANSDUCER FILM AND SAIDMATERIAL, SAID MATERIAL HAVING A LARGER ENERGY GAP TNAN SAIDPHOTOELECTRIC TRANSDUCER FILM, SAID PHOTOELECTRIC TRANSDUCER FILMCONTAINING ZNYCD1-YTE (0.1 Y 0.9) AS A MAIN COMPONENT, AND SAID
 2. Aphotoelectric transducer element and a target for an image pickup tubeusing said element according to claim 1, wherein said photoelectrictransducer film containing ZnyCd1-yTe (0.1 < or = y < or = 0.9) as themain component further contains indium added thereto.
 3. A photoelectrictransducer element and a target for an image pickup tube using saidelement according to claim 2, wherein said photoelectric transducer filmcontaining ZnyCd1-yTe (0.1 < or = y < or = 0.9) as the main componentcontains 0.02 to 3.2 atomic percent of indium added thereto.
 4. Aphotoelectric transducer element and a target for an image pickup tubeusing said element according to claim 1, wherein said photoelectrictransducer film containing ZnyCd1-yTe (0.1 < or = y < or = 0.9) as themain component further contains 30 mol% or less of a compound of In andTe added thereto.
 5. A photoelectric transducer element and a target foran image pickup tube using said element, comprising a photoelectrictransducer film, a transparent conductive film, a material interposedbetween said photoelectric transducer film and said transparentconductive film, and a heterojunction of said photoelectric transducerfilm and said material, said material having a larger energy gap thansaid photoelectric transducer film, said photoelectric transducer filmcontaining ZnyCd1-yTe (0 < or = y < or = 1) as a main component andfurther containing 30 mol percent or less of a compound of In and Teadded thEreto, said photoelectric transducer film having the formula(ZnyCd1-yTe (0 < or = y < or = 1))z(In2Te3)1-z (0.7<z<1), and saidmaterial containing ZnSxSe1-x(0 < or = x < or = 1) as a main component.6. A photoelectric transducer element and a target for an image pickuptube using said element according to claim 5, wherein x 0 and z 0.95. 7.A photoelectric transducer element and a target for an image pickup tubeusing said element, comprising a photoelectric transducer film, atransparent conductive film, a material interposed between saidphotoelectric transducer film and said transparent conductive film, anda heterojunction of said photoelectric transducer film and saidmaterial, said material having a larger energy gap than saidphotoelectric transducer film, said photoelectric transducer filmcontaining ZnyCd1-yTe (0.5 < or = y < or = 0.8) as a main component andfurther containing 30 mol percent or less of a compound of In and Teadded thereto, said photoelectric transducer film hhaving the formula(ZnyCd1-yTe (0.5 < or = y < or = 0.8))0.95 (In2Te3)0.05, and saidmaterial containing ZnSe as a main component.
 8. A photoelectrictransducer element and a target for an image pickup tube using saidelement according to claim 5, wherein x 0 and y 0.6.
 9. A photoelectrictransducer element and a target for an image pickup tube using saidelement, comprising a photoelectric transducer film, a transparentconductive film, a material interposed between said photoelectrictransducer film and said transparent conductive film, and aheterojunction of said photoelectric transducer film and said material,said material having a larger energy gap than said photoelectrictransducer film, said photoelectric transducer film containingZn0.6Cd0.4Te as a main component and further containing 30 mol percentor less of a compound of In and Te added thereto, said photoelectrictransducer film having the formula (Zn0.6Cd0.4Te)z(In2Te3)1-z (0.85 < or= z<1), and said material containing ZnSe as a main component.
 10. Aphotoelectric transducer element and a target for an image pickup tubeusing said element according to claim 5, wherein y 0.6 and z 0.95.
 11. Aphotoelectric transducer element and a target for an image pickup tubeusing said element according to claim 10, wherein x